practical 4 brief intro to the brain - north seattle...
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Lab 19
Cranial Nerves & Brain dissection
Today
• Intro to the brain• The cranial nerves• Human and sheep brain anatomy• Get to work• CLEAN UP
Practical 4
• Thurs 12/6• 50 points: about half brain models and half
book figures (with a few fresh brains too)• Know:
– List of brain parts on objectives (names and locations only; you will need to know functions on the exam though)
– The 12 cranial nerves: names, locations, & functions(shown in blue in this lecture)
Brief intro to the brainExternal structures• cerebral hemispheres• cerebrum• midbrain• cerebellum• pons• medulla• central sulcus• precentral gyrus• postcentral gyrus• lateral sulcus• longitudinal fissure• frontal lobe• parietal lobe• occipital lobe• temporal lobe
Internal structures: • corpus callosum• basal ganglia (nucleus)
– Caudate– Putamen
• internal capsule• thalamus• hypothalamus• hippocampus• amygdala• pineal gland• pituitary gland• reticular formation• fornix• substantia nigra• cingulate gyrus• optic chiasm• lateral ventricles• mammilary bodies• corpora quadrigemina
– inferior colliculus– superior colliculus
Figure 14–1
Major Regions and Landmarks Regions of the Adult Brain
• Telencephalon (cerebrum) – cortex, white matter, and basal nuclei
• Diencephalon – thalamus, hypothalamus, and epithalamus
• Mesencephalon –midbrain (brain stem)• Metencephalon – pons (brain stem),
cerebellum• Myelencephalon – medulla oblongata
(brain stem)
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Some terms
• nucleus: collection of neuron cell bodies in the CNS
• tract: collection of axons in the CNS• ganglia: collection of neuron cell bodies in
the PNS• nerve: collection of axons in the PNS
– Cranial nerves– Spinal nerves
Tour through the brain
• From caudal/inferior to rostral/superior
The Brain Stem
• Includes:– mesencephalon (midbrain)– pons– medulla oblongata– Note: some consider the diencephalon part of
the brain stem as well
Anatomy:Brain stem
Most cranial nerves are located in the brain stem
Posterior view Medulla Oblongata
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Cerebellum Cerebellum – side view
Mesencephalon Mesencephalon
Figure 14–5a
The Diencephalon
• Thalamus• Hypothalamus• Pineal gland• Pituitary gland
Telencephalon
• Cerebrum– Largest part of brain, includes huge wrinkly
cerebral hemispheres• Basal nuclei
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Figure 14–14b, c
The Basal Nuclei (Ganglia) Lateral Ventricles
Figure 14–11a
The Limbic System
Figure 14–12b
The Cerebral Cortex
4 Lobes:frontalparietaltemporaloccipital
Cerebral Cortex landmarks
• Lateral sulcus• Longitudinal fissure• Central sulcus• Precentral gyrus (primary motor)• Postcentral gyrus (primary sensory)• Association areas are for integrating
information
Figure 14–15a
Motor and Sensory Areas of the Cortex
• Central sulcus separates motor and sensory areas
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Cranial Nerves
Figure 14–18
Cranial Nerves• 12 pairs connected to brain
Cranial Nerves
Figure 13.5a
Cranial Nerves
• Twelve pairs of cranial nerves arise from the brain
• They have sensory, motor, or both sensory and motor functions (mixed)
• Each nerve is identified by a number (I through XII) and a name
• Four cranial nerves carry parasympathetic fibers that serve muscles and glands
3 main types of Cranial Nerves
Sensory nerves:– carry somatic (touch) or special sensory
informationMotor nerves:
– axons of somatic motor neuronsMixed nerves:
– mixture of motor and sensory fibers
Cranial Nerves
• I – Olfactory• II – Optic• III – Occulomotor• IV – Trochlear• V – Trigeminal• VI – Abducens
• VII – Facial• VIII – Vestibulococlear• IX – Glossopharyngeal• X – Vagus• XI – Accessory• XII – Hypoglossal
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Summary of Function of Cranial Nerves
Figure 13.5b
You need to learn:
• Names• Numbers• Locations• Main functions (in blue)
Lateral view
Anterior View
Figure 14–19
The Olfactory Nerves (I)
Olfactory Nerves (I)
• Don’t originate or enter brainstem• Primary function:
– special sensory (smell)• Arises from the olfactory epithelium• Passes through the cribriform plate of the
ethmoid bone• Fibers run through the olfactory bulb and
terminate in the primary olfactory cortex• Functions solely by carrying afferent
impulses for the sense of smellFigure 14–20
The Optic Nerves (II)
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Optic Nerves (II)
• Enter diencephalon• Primary function:
– special sensory (vision)• Arises from the retina of the eye• Optic nerves pass through the optic canals
and converge at the optic chiasm• They continue to the thalamus
(diencephalon) where they synapse
CNs III,IV,VI
• All motor only• All innervate eye muscles
Figure 14–21
The Oculomotor Nerves (III) Oculomotor Nerves (III)
• Primary function: – motor (many eyeball movements, pupil
constriction, controlling lens shape)• Origin:
– mesencephalon• Destination:
– somatic motor: 4 extrinsic eye muscles: – visceral motor: parasympathetic NS cell
bodies in the ciliary ganglion, got to intrinsic eye muscles
Figure 14–21
The Trochlear Nerves (IV) Trochlear Nerves (IV)
• Smallest CN• Primary function:
– motor (eye movement: looking down)• Origin:
– mesencephalon• Destination:
– superior oblique muscle (that’s it!)
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The Abducens Nerves (VI)
Figure 14–21
The Abducens Nerves (VI)
• Primary function: – motor (eye movement: looking to the side)
• Origin: – pons
• Destination:– lateral rectus muscle (just one eye muscle)
Figure 14–22
The Trigeminal Nerves (V) Trigeminal Nerves (V)
• Largest CN – it’s huge!• Primary function:
– mixed (sensory and motor) to face All sensory from face; motor for chewing
• Three branches– ophthalmic branch (sensory)– maxillary branch (sensory)– mandibular branch (sensory and motor)
• Destinations– sensory: sensory nuclei in pons
Figure 14–23
The Facial Nerves (VII) Facial Nerves (VII)
• Primary function: – mixed (sensory and motor) to faceMotor to facial muscles; taste
• sensory: – taste receptors on anterior 2/3 of tongue
• motor: – Facial muscles, parasympathetic to lacrimal
and salivary glands**Bell’s Palsy
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Figure 14–24
The VestibulocochlearNerves (VIII)
VestibulocochlearNerves (VIII)
• Primary function: special sensory – vestibular branch:
• balance and equilibrium– cochlear branch:
• hearing
• Origin: receptors of inner ear• Destination: nuclei in both pons and
medulla
Figure 14–25
The GlossopharyngealNerves (IX)
GlossopharyngealNerves (IX)
• Primary function: – mixed (sensory and motor) to head and neck Mainly: swallowing, some salivary gland function
• Origins:– sensory:
• posterior 1/3 of tongue• part of pharynx and palate• carotid bodies (blood pressure/CO2 sensors)
– motor: • motor nuclei of medulla
Figure 14–26
The VagusNerves (X) Vagus Nerves (X)
• Primary function: – mixed (sensory and motor) of thorax and
abdomen– Only CN that extends beyond head and neck– “Mr. parasympathetic” motor to para-NS– Runs outside of spinal cord to visceral organs– Originates in medulla
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Figure 14–27
The Accessory Nerves (XI) Accessory Nerves (XI)• Primary function:
– motor to muscles of neck and upper back• Origin:
– motor nuclei of spinal cord and medulla oblongata• Two roots:
– The spinal root passes upward into the cranium via the foramen magnum
– The accessory nerve leaves the cranium via the jugular foramen
• Destinations:– voluntary muscles of palate, pharynx, and larynx– sternocleidomastoid and trapezius muscles
Figure 14–27
The Hypoglossal Nerves (XII) Hypoglossal Nerves (XII)
• Primary function: – motor (tongue movements)
• Origin: – motor nuclei of medulla
• Destination: – muscles of tongue which aid in speech
Gross Anatomy of the human brain Human brain
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Midsagittal Coronal
InferiorView
Sheep brain
Sheep brain inferior view
Midsagittal
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Anterior View
Follow instructions in lab book
• look at the meninges• start by examining the external brain
– Ventral surface first, then dorsal• then look internally without cutting (fig 19.12)• cut it midsagittally to see inside• Try a coronal cut to see what you can find
• Review Sheet due next Thursday
To find:• Meninges• Cranial nerves I – XII (?)• fissures and sulci on
surface, lobes• pineal gland• corpora quadrigemina
(part of midbrain)• midbrain• pons• medulla• cerebellum • mamillary body (just one)• optic chiasm
• corpus callosum (central)• fornix• lateral ventricles• choroid plexus (inside
ventricles)• hypothalmus• “pituitatry gland” (hangs
off hypothalamus• arbor vitae (inside
cerebellum)
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